The proposed research will investigate galvanic-induced and spontaneous body sway in normal and pathological subjects. We will study the waveform of the normal and abnormal galvanic body-sway response, the effect of subject stability on the response, and the effect of varying stimulus parameters on the abnormal response. Information obtained from these experiments will be used to improve upon the already established ability of the galvanic body-sway test to separate vestibular from retrovestibular pathology. A new instrument for quantitatively controlling subject stability will be used to investigate the relationship between subject stability and spontaneous sway. This information will be applied to the development of a quantitative Romberg test. We also plan to utilize the galvanic test to investigate disease entities which would be better understood if it were known whether or not vestibular-nerve pathology is present. The disease entities to be investigated are sudden deafness, vestibular neuronitis, and Bell's palsy.